1. Field of the Invention
The present invention relates generally to apparatus used for mounting boom structures to movable agricultural vehicles. In particular, the present invention relates to a breakaway apparatus that constrains movement of an extended boom arm to reduce stress on the boom arm and mounting apparatus when loads are placed on the boom arm during operation of the moving vehicle.
2. Description of the Prior Art
Field crops are frequently treated (sprayed) with fluids by a movable agricultural implement. The implement may be a trailer or self-propelled vehicle that carries a fluid reservoir and has a structure for transferring the fluid from the reservoir to a device through which the fluid is sprayed onto the crops. A typical fluid transfer structure is a boom arm which extends laterally outwardly from the implement frame and carries a fluid pathway from the reservoir to a plurality of spray nozzles positioned on the boom arm. Typical examples of such implements are shown in the following U.S. Pat. Nos.:
______________________________________ U.S. Pat. No. INVENTOR ISSUE DATE ______________________________________ 3,147,925 Compton 8 Sept. 1964 3,927,032 Robison et al. 23 Dec. 1975 4,138,063 Batts 6 Feb. l979 4,200,255 Schmidt et al. 29 Apr. 1980 4,221,353 Kuhn et al. 9 Sept. 1980 4,344,572 Tyler 17 Aug. 1982 4,634,051 Dudley 6 Jan. 1987 4,834,249 Dahl 30 May 1989 ______________________________________
A typical boom arm is an elongated resilient member which is pivotally mounted to the side or rear of a vehicle frame and extends outward in a substantially horizontal fashion. Typically, a boom arm extends out from each side of the vehicle, and the boom arms are rotatable (to some degree) about the vehicle frame in both horizontal and vertical directions to position the boom arms as desired relative to the field and vehicle frame. The mounting structure tends to maintain each boom arm in a selectively fixed lateral orientation (spraying position) to facilitate the spraying of the fluids onto the field.
Occasionally, objects in the field (e.g., rocks, fences, trees, etc.) obstruct the path of an extended boom arm. This places stress on the boom arm and mounting apparatus and/or impairs the functioning of the boom arm structure. Therefore, the typical mounting apparatus includes a breakaway mechanism that permits the release of the boom arm from a lateral spraying position to allow rearward horizontal rotation of the boom arm relative to the vehicle frame. The release of the arm thus diminishes the stress placed on the boom arm and mounting apparatus. The breakaway mechanism may also include a return mechanism which returns the boom arm to the spraying position, from which the boom arm has "broken away" after contacting the obstruction.
Spra-Coupe sprayers manufactured and sold by the Melroe Company of Fargo, N.D. have a pair of booms pivotally mounted to opposite sides of a frame by boom mounting or attaching plates. A pair of metal main or actuator mounting plates, one of which is associated with each boom mounting plate, are pivotally mounted to the frame between the boom mounting plates. Actuators mounted between associated boom and actuator mounting plates are used to drive the booms between folded travel positions and extended spraying positions. The actuator mounting plates are coupled together by a spring and shock absorber. When one of the booms encounters an obstruction, the boom is swung rearwardly. This motion is coupled through the actuator to the actuator plate which pivots from a stop position against a metal plate to a breakaway position compressing the shock absorber and stretching the spring. Once the obstruction is cleared, the spring returns the actuator plate to its stop position against the metal plate thereby forcing the boom to its spray position. This breakaway and return action of one boom can result in undesired motion of the other boom. Undue stress can also be placed on the frame, metal stop and actuator plate when the boom is returned to its spray position.
It is evident that there is a continuing need for improved spray boom breakaway systems. The breakaway system must be effective at preventing boom damage when obstructions are encountered, yet prevent excessive stress on the mounting frame and booms during return actions. To be commercially viable, the breakaway system must also be rugged, reliable and of relatively simple design.